Twist beam suspension with y-beam control arm

ABSTRACT

A suspension arrangement for interconnecting a frame and an axle in a vehicle includes a control arm having a first beam and a second beam in parallel, spaced relation, each beam having a first end with a single arm and a second end with an upper arm and a lower arm to define a Y-shape, the first end being pivotally connectable to a vehicle frame, and the second end being connectable to a vehicle axle disposed between the upper and lower arms, and a bushing arrangement mountable to the vehicle axle, the bushing arrangement having an upper portion connecting between the upper arms of the first beam and second beam and a lower portion connecting between the lower arms of the first beam and second beam.

FIELD OF THE INVENTION

The invention is directed to vehicle suspensions, in particular heavyvehicle suspensions. More particularly, the invention is directed to arear suspension arrangement for interconnecting a frame and axle in avehicle.

BACKGROUND AND SUMMARY

Many rear air suspensions allow twist in the axle during roll events(opposite wheel travel in the vertical direction) to provide rollstiffness. However, because of the manner in which the axle is attachedto such suspensions, unwanted forces are transferred to the axle.

One approach to a solution is shown in U.S. Pat. No. 4,310,171 toMerkle. Merkle shows a vehicle axle attachment having a control armhaving two parallel plates shaped to form horizontally spaced lugs atone to attach to the vehicle hangar bracket and vertically spaced lugsat the opposite end to attach to the axle. The vertically spaced lugsare rigidly connected to the axle by way of a flange. With a rigidconnection, the roll rate of this arrangement is fixed.

A suspension arrangement in accordance with the invention includes acontrol arm provided as a beam having a first end with a single arm anda second end with an upper arm and a lower arm diverging to define aY-shape, the first end being connectable to a vehicle frame, and thesecond end being connectable to a vehicle axle disposed between theupper and lower arms. A bushing arrangement mounts the arms to thevehicle axle, the bushing arrangement having an upper portion connectingto the upper arm and a lower portion connecting to the lower arm, thebushing having a selected rate.

The suspension according to the invention improves the transfer oftwisting forces to the axle by constraining the axle between two arms ofthe control arm. The axle is twisted about the center of torsion,allowing increased twist to the axle without the introduction of anextra bending moment in the axle. The invention advantageously addsadjustment of the response of the suspension by way of the axlebushings.

According to another aspect of the invention, the control arm is formedof a first beam and a second beam in parallel, spaced relation, thefirst beam and second beam being interconnected to the axle by thebushing arrangement. The spacing may be varied, according to theinvention, to provide the desired mechanical advantage for twisting theaxle. The first beam and second beam are relatively thin plate membersthat provide a weight advantage in the assembly while providingsufficient strength and stiffness in the vertical direction. Inaddition, forming the first beam and second beam as thin plates providessome lateral flexibility to the suspension assembly for accommodatinglateral suspension events.

The invention thus provides an improvement in roll rate by a control armthat is much stiffer in the vertical direction than in the lateraldirection.

According to the invention, the first beam and second beam areinterconnected only by the axle bushing arrangement and a second bushingarrangement mounting the beams to the vehicle frame.

According to another aspect of the invention, the first beam and secondbeam are connected to form the control arm with the axle end bushingarrangement disposed between the respective upper arms and lower arms.

Preferably, the bushing arrangement includes two upper bushings and twolower bushings.

According to another aspect of the invention, the rate of the bushingsthat attach the beam to the axle may be varied to influence certainsuspension characteristics. For example, making the two top bushingsstiffer in the fore/aft direction and relatively softer in the verticaldirection and making the bottom bushings softer in the fore aftdirection and relatively stiffer in the vertical direction can improveroll steer, lateral stiffness, roll rate, toe stiffness and camberstiffness.

According to yet another aspect of the invention, the first beam andsecond beam each include a plate section and flanges extendingperpendicularly from edges of the plate section, wherein the first beamand second beam are mutually disposed with the respective flangesextending in opposite directions.

According to another aspect of the invention, the suspension arrangementfurther includes a hanger mountable to the frame, the first end of thecontrol arm being pivotally mounted to the hanger.

According to yet another aspect of the invention, the suspensionarrangement further includes a spring mountable between the axle and theframe. The spring may be disposed between a seat on an arm mountable toand extending from the axle and a bracket mountable to the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the followingdetailed description read in conjunction with the appended drawings, inwhich:

FIG. 1 is a side view of a suspension arrangement in accord with theinvention;

FIG. 2 is a perspective view of the suspension arrangement of FIG. 1;

FIG. 3 is a perspective view of an embodiment of a top bushing devicefor connecting control arms to an axle;

FIG. 4 is a perspective view of one embodiment of a bottom bushingdevice and spring arm for connecting a control arm to the axle andsupporting a spring;

FIG. 5 is an example of a tuned bushing which may be used in thesuspension arrangement of the invention; and,

FIG. 6 is another example of a tuned bushing.

DETAILED DESCRIPTION

FIG. 1 is a side view of a suspension arrangement in accordance with theinvention. FIG. 2 shows a perspective view of the suspension arrangementof FIG. 1. The suspension arrangement connects a vehicle frame rail 10and vehicle axle 12. In FIG. 2, a vehicle frame rail 11 of the oppositeside of the frame is shown, while the frame rail in the foreground ofthe drawing has been removed for clarity. An assembly of the suspensionarrangement of the invention would be mounted on each end of the axle toconnect each end of the axle to the respective frame rail. FIG. 2illustrates in detail one such assembly; only parts of the opposite sideare shown to avoid over-complicating the figure.

The suspension interconnects a vehicle axle 12 to the vehicle frame 10.The axle 12 in the illustration is a driven axle and includes a gearhousing 14 which connects to an output shaft of a transmission (notillustrated). The axle 12 also includes a spindle 16 for mounting awheel or wheels to the axle. The gear arrangement in the gear housing 14transmits driving force to the spindle to turn the wheels.

The suspension includes a control arm 20 extending between the vehicleframe 10 and the axle 12. In the figures, the control arm 20 is formedby two, parallel beams 22, 24. The embodiment of two parallel beams 22,24 is preferred because it provides relatively light weight control armwith sufficient strength and vertical stiffness and provides aredundancy in the event one beam is disabled. The invention, however,contemplates a single beam forming the control arm 20, and the followingdescription should be understood in that context. The beams 22, 24, areeach shaped in a Y configuration, having a first end 30 with a singlearm and a second end with two diverging arms, an upper arm 32 and alower arm 34. The terms “upper” and “lower” are relative to theorientation of the beams 22, 24 when mounted on a vehicle frame, asportrayed in the figures. Each beam 22, 24 is a substantially planarsheet or plate member and the outer edges 28 are bent or formedperpendicularly to form flanges for stiffening the beam. If weight isnot an important consideration, the beam may be formed as a plate memberof sufficient thickness to provide needed stiffness. Alternatively, thebeam may be formed as a box member, having side walls and a perimeterwall enclosing a space.

The spacing between beam 22 and beam 24 forming the control arm 20 maybe selected to provide a desired mechanical advantage in transferringforce to the axle 12. In addition, the depth of the outer edges 28 ofthe beams 22, 24 may be selected to provide a desired amount of lateralstiffness in the beams.

The first end 30 of the control arm 20 is mounted for vertical pivotingmovement to a hanger bracket 40 that is attached to the vehicle frame. Ahangar bushing arrangement 42 may be used.

According to the invention, the axle 12 is mounted to the control arm 20between the divergent upper arm 32 and lower arm 34. An upper bushingassembly 50, shown in the perspective view in FIG. 3, connects the upperarms 32 of the control arm 20 to the axle 12.

A lower bushing assembly 60, shown in perspective view in FIG. 4,connects the lower arms 34 of the control arm 20 to the axle 12. Theupper bushing assembly 50 and lower bushing assembly 60 are connected tothe axle and clamp the axle between them by U-bolts 44 (only one isvisible in FIG. 2).

The upper bushing assembly 50, referring to FIG. 3, includes a plate 52that engages the axle 12, and has two shoulder and trough formations 54formed in the plate to engage the U-bolt 44 for securing the upperbushing to the axle. Two bushing mounts 56 are formed in parallel andupstanding on the plate 52. The bushing mounts 56 have holes 58 that aresubstantially parallel to the axle. The bushing mounts 56 carry aselected bushing (not illustrated) in the respective holes 58. The upperarms 32 of the control arm 20 are mounted to the upper bushing assembly50 by way of fasteners inserted through the bushings in the bushingmounts 56.

In the illustrated embodiment, the beams 22, 24 are interconnected atthe first end 30 of the control arm 20 and at the diverging upper arm 32and lower arm 34, but not therebetween. This provides a degree oflateral flexibility, as discussed below.

Turning to FIG. 4, the lower bushing assembly 60 includes a seat 62 toengage the bottom of the axle 12. The seat 62 is between bars 64 havingmounting holes which accept the U-bolt 44 for securing the lower bushingassembly 60 to the axle 12 as described above. The lower bushingassembly 60 also includes two bushing mounts 66 disposed below the seat62. The bushing mounts 66 are formed with holes parallel to the axle, asin the upper bushing assembly 50, and carry a selected bushing (notshown). The lower arms 34 of the control arm 20 are mounted to the lowerbushing assembly 60 by way of fasteners inserted through the bushings inthe bushing mounts 66.

According to the invention, bushings are preferably formed ascylindrical members of resilient material sized and shaped to fit thebushing mounts 56, 66, and the material may be selected for rate orstiffness. Thus, the control arm 20 is attached to the axle with aselected amount of resilience. According to another aspect of theinvention, the bushings in each of the bushing mounts 56, 66, may beindividually selected, allowing, for example, the upper bushing assembly50 to have the same or a different bushing rate than the lower bushingassembly 60, or allowing the two bushings in the each bushing assembly50, 60 to have the same or different rates. Further, each bushing mayhave a variable rate to effect changes in the suspensioncharacteristics, that is, a bushing may be made to have a different ratein one direction than in another. As shown in FIG. 5, one known variablerate bushing 80 employs voids 82 placed in the bushing in a selectedportion or portions to soften that portion relative to the rest of thebushing. The voids 82 result in the bushing 80 being softer in adirection of the voids, in the figure along axis A. Alternatively, FIG.6 shows a cross section of a bushing 90 formed of different materials, arelatively stiffer material 92 and a relatively softer material 94. Thebushing 90 is relatively stiffer along the axis marked A than along theaxis marked B. By selectively orienting a variable rate bushing 80, 90,in the bushing mount 56, 66, the directional rate of the bushingassembly may be tuned. Other arrangements are possible, for example, abushing may be made with a stiffer material on one half and a softermaterial on the other half to provide different rates in oppositedirections along the same axis.

Tuning the rate of the bushing assembly can affect the suspensioncharacteristics. For example, making the two top bushings relativelystiffer in the fore/aft direction and relatively softer in the verticaldirection and the bottom bushings relatively softer only in the fore aftdirection and relatively stiffer in the vertical direction, which may bedone with the variable bushings 80 or 90, can improve roll steer,lateral stiffness, roll rate, toe stiffness and camber stiffness.

The spacing and location of the upper bushing mounts 56 and lowerbushing mounts 66 on the respective bushing assembly may be selected toorient the axle at a particular angle to set the pinion angle.

Turning again to FIG. 4, the lower bushing assembly 60 includes a beam70 extending from the seat 62 in a direction that, when mounted, isopposite the control arm 20. The beam 70 includes mounting flanges 72for a damper 74 (shown in FIGS. 1 and 2), which connects between thebeam and the vehicle frame. At the end of the beam 70 is a spring seat76 to support a spring member, illustrated in FIGS. 1 and 2 as an airspring 78. As may be seen in FIG. 1, the air spring 78 is mountedbetween the beam 70 and the vehicle frame.

By constraining the axle between the upper arm 32 and lower arm 34 ofthe control arm 20, any twist applied to the axle is applied about itsaxial center and an extra bending moment is not introduced during a rollevent. By contrast, in conventional control arm suspensions, whichconnect to the axle on one side only (e.g., typically top or bottom),there is a bending introduced when the axle is twisted during a rollevent.

The profile of the control arm 20 with its relatively deep verticaldimension (perpendicular to the axle axis) and relatively narrow lateraldimension (parallel to the axle axis) make it stiffer in the verticaldirection than in the lateral direction. The vertical stiffness makesthe control arm 20 effective in transferring load into the frame duringa roll event. By being less stiff in the lateral direction, the controlarm decreases the amount of preload going into the lateral torque rod.The lateral torque rod 80 may be attached between the torque rod bracket18 seen in FIG. 1 and the frame rail 11.

The invention has been described in terms of preferred principles,embodiments, and components, however, those skilled in the art willunderstand that substitutions of equivalents may be made withoutdeparting from the scope of the invention as defined by the appendedclaims.

1. A suspension arrangement for interconnecting a vehicle frame andaxle, comprising: a control arm comprising a beam having a first endwith a single arm and a second end with an upper arm and a lower armdiverging to define a Y-shape, the first end being connectable to avehicle frame, and the second end being connectable to a vehicle axledisposed between the upper and lower arms; a bushing arrangementmountable to the vehicle axle, the bushing arrangement having an upperbushing connecting to the upper arm and a lower bushing connecting tothe lower arm, the upper bushing and lower bushing each having aselected rate.
 2. The suspension arrangement of claim 1, wherein thecontrol arm comprises a first beam and a second beam in parallel, spacedrelation.
 3. The suspension arrangement of claim 2, wherein the firstbeam and second beam each include a plate and flanges extendingperpendicularly from edges of the plate, wherein the first beam andsecond beam are mutually disposed with the respective flanges extendingin opposite directions.
 4. The suspension arrangement of claim 2,wherein the first beam and second beam are connected with the bushingarrangement between the respective upper arms and lower arms.
 5. Thesuspension arrangement of claim 1, wherein the bushing arrangementincludes two upper bushings and two lower bushings.
 6. The suspensionarrangement of claim 5, wherein each of the two upper bushings and eachof the two lower bushings have a selected rate.
 7. The suspensionarrangement of claim 1, wherein the bushing arrangement comprises aplurality of bushings, each bushing having a variable rate.
 8. Thesuspension arrangement of claim 1, further comprising a hanger mountableto the frame, the first end being pivotally mounted to the hanger. 9.The suspension arrangement of claim 1, further comprising a springmountable between a seat on a member mountable to and extending from theaxle and the frame.
 10. The suspension arrangement of claim 1, whereinthe single arm, upper arm and lower arm of the beam define a plane, andwherein the beam is stiffer parallel to the plane than perpendicular tothe plane.
 11. A suspension arrangement for interconnecting a frame andan axle in a vehicle, comprising: a control arm comprising a first beamand a second beam in parallel, spaced relation, each beam having a firstend with a single arm and a second end with an upper arm and a lower armto define a Y-shape, the first end being pivotally connectable to avehicle frame, and the second end being connectable to a vehicle axledisposed between the upper and lower arms; and, a bushing arrangementmountable to the vehicle axle, the bushing arrangement having an upperportion connecting between the upper arms of the first beam and secondbeam and a lower portion connecting between the lower arms of the firstbeam and second beam, the upper portion and lower portion of the bushingarrangement each having a selected rate.
 12. The suspension arrangementof claim 11, wherein the first beam and second beam each include a platesection and flanges extending from edges of the plate section, whereinthe first beam and second beam are mutually disposed with the respectiveflanges extending in opposite directions.
 13. The suspension arrangementof claim 11, wherein the bushing arrangement comprises a plurality ofbushings, each bushing having a variable rate.
 14. The suspensionarrangement of claim 11, wherein the bushing arrangement includes twoupper bushings and two lower bushings.
 15. The suspension arrangement ofclaim 14, wherein each of the two upper bushings and two lower bushingshas a selected rate.
 16. The suspension arrangement of claim 12, furthercomprising a hanger mountable to the frame, the first ends of the firstbeam and second beam being pivotally mounted to the hanger.
 17. Thesuspension arrangement of claim 12, further comprising a springmountable between the axle and the frame.
 18. The suspension arrangementof claim 17, wherein the spring is disposed between a seat on an armmountable to and extending from the axle and a bracket mountable to theframe.